Cut-resistant knitted fabric

ABSTRACT

A cut-resistant knitted fabric comprising a para-aramid yarn knitted with a composite yarn to provide the fabric with a sandwich knit structure. The composite yarn is comprised of a reinforcing filament, a polyolefin filament and a polyester filament. The fabric preferably comprises 10 to 90% of the para-aramid yarn, which is preferably poly-paraphenylene terephthalamide yarn. A method for producing such a cut-resistant fabric is also described. This combination of yarns and sandwich knit structure provides a relatively light and flexible with a cut resistance and anti-slash performance equivalent to current protective garment fabrics produced using woven fabrics that are two to three times heavier.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims foreign priority benefit of BritishPatent Application No. 0418521.1, filed Aug. 19, 2004, the entirecontents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention generally relates to a knitted fabric, and moreparticularly relates to a cut-resistant knitted fabric for use in, forexample, cut-resistant or slash-resistant clothing.

BACKGROUND

Many different applications, such as military, security and industrialapplications, require protective clothing exhibiting cut or slashresistance. By way of example, workers in the glass manufacturingindustry must wear clothing to protect them from cuts whilst handlingpieces of glass. Statutory requirements are in place to ensure that suchclothing meets the required safety criteria. Annex II of PPE (PersonalProtective Equipment) directive 98/868/EEC provides a classificationsystem (EN388:2003 6.2) for protective fabrics according to their bladecut resistance having levels 0 (indicating a low cut resistance) to 5(indicating a high cut resistance).

Knitted fabrics currently employed in protective clothing used in theglass industry typically exhibit an EN388:2003 6.2 blade cut resistanceof around 2. It is desirable to provide fabrics having a much higherblade cut resistance, such as level 4, or more preferably level 5.Efforts to provide a fabric exhibiting increased blade cut resistancehave so far resulted in fabrics which are significantly heavier, lessflexible and thereby less comfortable to wear than current fabricsexhibiting level 2 cut resistance. An object of the present invention isto obviate or mitigate the aforementioned problems and to provide afabric exhibiting higher blade cut resistance than current protectivefabrics but which is not significantly heavier or less flexible thancurrent fabrics.

Therefore, there is a still a need in the industry to provide animproved cut-resistant knitted fabric. The present invention meets thisneed and provides other benefits and advantages in a novel and unobviousmanner.

SUMMARY

The present invention relates generally to a cut-resistant knittedfabric. While the actual nature of the invention covered herein can onlybe determined with reference to the claims appended hereto, certainforms of the invention that are characteristic of the preferredembodiments disclosed herein are described briefly as follows.

According to a first aspect of the present invention there is provided acut-resistant knitted fabric comprising a para-aramid yarn knitted witha composite yarn comprised of a reinforcing filament, a polyolefinfilament and a polyester filament to provide said fabric with a sandwichknit structure.

A second aspect of the present invention provides an item of clothingcomprising a fabric according to the first aspect of the presentinvention.

According to a third aspect of the present invention there is provided amethod for producing a cut-resistant knitted fabric comprising knittinga para-aramid yarn and a composite yarn comprised of a reinforcingfilament, a polyolefin filament and a polyester filament to provide saidfabric with a sandwich knit structure.

It is one object of the present invention to provide an improvedcut-resistant knitted fabric. Further objects, features, advantages,benefits, and further aspects of the present invention will becomeapparent from the drawings and description contained herein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended. Any alterations and further modificationsin the illustrated devices, and any further applications of theprinciples of the invention as illustrated herein, are contemplated aswould normally occur to one skilled in the art to which the inventionrelates.

This combination of yarns and sandwich knit structure provides arelatively light and flexible fabric of a weight similar to that of aconventional non-protective garment fabric but with a cut resistanceequivalent to current protective garment fabrics produced using wovenfabrics that are two to three times heavier. This results in a muchimproved comfort level for users wearing garments made from theinventive fabric. It is envisaged that the composite yarn may compriseany desirable number of different reinforcing, polyolefin and/orpolyester filaments. In particular, the composite yarn may comprise twoor more different polyester filaments. The sandwich knit structureprovides the fabric with opposite front and back surfaces in which thedesired proportion of para-aramid yarn to composite yarns can beprovided. Thus it is possible to provide the fabric with face and backsurfaces in which the face surface is predominantly comprised of thecomposite yarn and the back surface is predominantly comprised of thepara-aramid yarn. In this way, the fabric can be used to produce an itemof clothing in which, for example, the back (predominantly para-aramidyarn containing) surface is provided on the inside of the item ofclothing so as to be preferentially in contact with a wearer's skin andthe face (predominantly composite yarn) surface is provided on theoutside of the item of clothing to minimise skin contact.

Preferably the fabric comprises 10 to 90% of the para-aramid yarn. Morepreferably the fabric comprises 25 to 75% of the para-aramid yarn. Mostpreferably the fabric comprises approximately 60% of the para-aramidyarn.

The fabric may comprise 10 to 60% of the composite yarn, more preferably20 to 50% and most preferably approximately 40% of the composite yarn.

Any appropriate percentage ratio of the para-aramid yarn to thecomposite yarn in the inventive fabric may be used, however, preferredpercentage ratios lie in the range 90-10 (para-aramid yarn):10-90(composite yarn). Further preferred percentage ratios of the para-aramidyarn to the composite yarn in the fabric lie in the range 75-25:25-75,with the most preferred percentage ratio of the para-aramid yarn to thecomposite yarn in the fabric being approximately 60:40.

Although any suitable para-aramid may be used, a preferred para-aramidis poly-paraphenylene terephthalamide, which is marketed under theregistered trademark Kevlar®. The para-aramid yarn may possess a yarncount of between 5 and 100 NM, more preferably in the range 20 to 70 NMand most preferably approximately 40 NM. The para-aramid yarn comprisesa fiber or filament possessing a fineness preferably in the range 0.5 to15 decitex, more preferably in the range 1 to 3 dtex, and mostpreferably approximately 1.7 decitex. It will be appreciated that thepara-aramid yarn typically comprises a plurality of such fibers orfilaments.

Any appropriate arrangement of reinforcing filament and polyolefinfilament may be employed in the composite yarn. However, it isparticularly preferred that the composite yarn comprises the polyolefinfilament wrapped around the reinforcing filament. Such an arrangementmay be considered as the reinforcing filament forming a core with thepolyolefin filament wrapped around the core in a substantially helicalarrangement. Wrapping the polyolefin filament around the reinforcingfilament core in this way can induce undesirable helical strain withinthe combined polyolefin/reinforcing filament structure. It is thereforedesirable to incorporate further filament or filaments arranged in anappropriate manner with respect to the polyolefin and reinforcingfilaments to help reduce this induced strain. Thus, it is preferred thatthe composite yarn comprises the polyester filament(s) wrapped aroundthe polyolefin and reinforcing filaments.

The composite yarn count can be selected depending upon the propertiesand intended applications for the final fabric incorporating the yarn.It is therefore preferred that the composite yarn possesses a resultantyarn count in the range 100 to 2000 decitex, more preferably in therange 200 to 1000 decitex and yet more preferably in the range 300 to400 decitex. It is most preferred that the composite yarn possesses aresultant yarn count of approximately 365 decitex.

The percentage composition of the various filaments comprised in thecomposite yarn can also be chosen to suit a particular application. Thusthe composite yarn may comprise up to approximately 50% of thereinforcing filament, more preferably up to approximately 25% and mostpreferably approximately 12.5% of the reinforcing filament. Moreover,the composite yarn preferably comprises up to approximately 75% of thepolyolefin filament, more preferably up to approximately 60% and mostpreferably approximately 52.5% of the polyolefin filament. Furthermore,it is preferred that the composite yarn comprises up to approximately50% of polyester filament, more preferably up to approximately 40% ofpolyester filament, yet more preferably approximately 35% of polyesterfilament.

When the most preferred fabric composition is employed, i.e. apercentage ratio of the para-aramid yarn to the composite yarn in thefabric of approximately 60:40, it is preferred that the fabric comprisesapproximately 5% of the reinforcing filament, approximately 14% of thepolyester filament and approximately 21% of the polyolefin filament.

The reinforcing filament is preferably a fiberglass filament or a metalfilament, which may be a stainless steel filament.

The fiberglass filament preferably possesses a Denier in the range 10 to100, more preferably 25 to 75 or yet more preferably a Denier ofapproximately 50. Preferably the polyolefin filament possesses a Denierin the range 100 to 500, 200 to 250 or approximately 215. Particularlypreferred polyolefin filaments for use in the composite yarn aremarketed under the registered trademarks Spectra® and Dyneema®. It ispreferred that the polyester filament possesses a Denier in the range 25to 200, 50 to 100 or approximately 70. Whilst any one of a number ofdifferent polyester filaments may be used, a preferred polyesterfilament is a polyethyleneterephthalate filament.

Many different types of knitted sandwich structure are known and may beused in accordance with this aspect of the present invention, however,preferably the sandwich structure of the fabric is selected from a groupconsisting of a weft knitted sandwich structure, a warp knitted sandwichstructure and a flat bed knitted sandwich structure.

The weight of the fabric can be selected to suit a particularapplication. Preferably the fabric preferably has a weight in the range100 to 700 g/m², more preferably in the range 200 to 500 g/m², yet morepreferably in the range 300 to 350 g/m², and most preferably in therange 320 to 330 g/m².

An important property of the inventive fabric is its resistance to beingslashed or cut using an implement having a sharp edge such as a knife ora piece of glass. Annex II of PPE directive 98/868/EEC provides a set ofclassifications for materials according to their abrasion resistance,blade cut resistance, tear resistance and puncture resistance. A fabricaccording to the first aspect of the present invention was tested inaccordance with the PPE directive and achieved an EN388 6.2 blade cutresistance index of 59, which is around three times greater than theindex required to be awarded the top level 5 for blade cut resistance.It is preferred that the fabric exhibits a blade cut resistance of atleast 4 and preferably level 5 on the EN388:2003 6.2 scale.

When the fabric of the present invention has been incorporated in to anitem of clothing it is preferred that the fabric comprised in the itemof clothing is arranged such that an inner surface of the item ofclothing configured to be in contact with a wearer is predominantlycomprised of the para-aramid yarn and an opposite outer surface of theitem of clothing is predominantly comprised of the composite yarn.

Preferably the yarns are knitted employing a method selected from agroup consisting of weft knitting, warp knitting and flat bed knitting.The yarns may be knitted in a single or double jersey style. It ispreferred that at least one of the yarns is produced using a methodselected from a group consisting of ring spinning, core spinning,wrapping and folding. The yarns and the fabric may be colored anydesirable color using any appropriate method during the production ofthe fabric. For example, at least one of the yarns may be dyed prior toknitting. Finishing of the fabric preferably comprises the step ofwashing the fabric at a temperature of up to approximately 130° C., morepreferably at a temperature of approximately 100° C. It is envisagedthat an item of clothing, such as a sweatshirt, t-shirt, balaclava orpiece of underwear, comprised of the inventive fabric should be washedas required after wearing at a temperature not exceeding around 40° C.Moreover, such an item of clothing should not be bleached, dry cleanedor tumble dried and should be ironed using a low temperature iron.

An embodiment of the present invention will now be described withreference to the following non-limiting Example:

EXAMPLE

Production Parameters

Yarns

-   1. 1/40 Nm, 100% Kevlar® 1.7 dtex, 38 mm, short staple spun.-   2. 365 dtex combination hollow spindle yarn—core 900 fiberglass    filament (50 Den), bottom cover Spectra® 215 Den filament, middle    and top covers 70 Den textured polyester filament.    Knitting-   Machine: Wildt Mellor Bromley model 9/MSJ749    -   30 ins diameter, 18 gg, 48 feeder, 1728+1728 needles-   Speed: 10 rpm.-   Production: at 3.5 kg/hr.

Machine Settings Feeders Dial Feeder: 1 2 3 4 5 6 B B miss A A missYarn: 1 1 2 1 1 2 Cylinder Feeder: 1 2 3 4 5 6 A miss B B miss A Yarn: 12 1 1 2 1 Knock Over Settings Dial: 1 2 3 4 5 6 30  40  15  30  40  15 Cylinder: 1 2 3 4 5 6 30  20  40  30  20  40 Tape Drive

-   Top row: 2 ins—16, yarn 1. Tapes closed.-   Bottom row: ½ ins—41, yarn 2. Run with tapes open.    Fabric Tension Medium Tight.    Finishing

Slit, light scour, stenter at 100° C. to natural width and weight.

Results

Fabric Properties

The properties of fabric produced using the production parameters setout in the Example are as follows:

-   Composition: 60% para-aramid;    -   21% polyolefin; 14% polyester; 5% fiberglass.-   Weight: 320/330 g/m².-   Width: 155/165 cm.    Fabric Performance

The sample of fabric produced as described in the Example exhibited thefollowing performance when tested in accordance with Annex II of PPEdirective 98/868/EEC:

-   EN388 6.1 Abrasion resistance level: 0    -   6.2 Blade cut resistance level: 5    -   6.3 Tear resistance level: 4    -   6.4 Puncture resistance level: 2

The fabric achieved a blade cut resistance index of 59, equating to ablade cut resistance of level 5, which is the highest level achievableunder PPE directive 98/868/EEC.

It will be understood that numerous modifications can be made to theembodiments of the invention described above without departing from theunderlying inventive concept and that these modifications are intendedto be included within the scope of the invention. For example, thepercentage composition of the fabric and the composite yarn can each bechosen to suit any given application. The fabric can be used to produceany desirable item of clothing, although it is envisaged that theinventive fabric would be eminently suitable to produce anti-slashclothing for use in military, security and industrial applications (suchas the glass manufacturing and automotive industries). For example, thefabric may be comprised in linings for anti-slash jackets, armprotectors, cuff protectors, aprons and trousers, or in anti-slashpullovers, sweatshirts, balaclavas and underwear.

1. A cut-resistant knitted fabric, comprising: a para-aramid yarnknitted with a composite yarn comprised of a reinforcing filament, apolyolefin filament and a polyester filament to provide said fabric witha sandwich knit structure.
 2. A fabric according to claim 1, wherein thefabric comprises 10 to 90% of the para-aramid yarn.
 3. A fabricaccording to claim 1, wherein the fabric comprises approximately 60% ofthe para-aramid yarn.
 4. A fabric according to claim 1, wherein thefabric comprises 10 to 60% of the composite yarn.
 5. A fabric accordingto claim 1, wherein the fabric comprises approximately 40% of thecomposite yarn.
 6. A fabric according to claim 1, wherein thepara-aramid is poly-paraphenylene terephthalamide.
 7. A fabric accordingto claim 1, wherein the para-aramid yarn possesses a yarn count ofbetween 5 and 100 NM.
 8. A fabric according to claim 1, wherein thepara-aramid yarn comprises a fiber or filament possessing a fineness inthe range 0.5 to 15 decitex.
 9. A fabric according to claim 1, whereinthe composite yarn comprises the polyolefin filament wrapped around thereinforcing filament.
 10. A fabric according to claim 1, wherein thecomposite yarn comprises the polyester filament wrapped around thepolyolefin filament and the reinforcing filament.
 11. A fabric accordingto claim 1, wherein the composite yarn possesses a resultant yarn countin the range 100 to 2000 decitex.
 12. A fabric according to claim 1,wherein the composite yarn possesses a resultant yarn count ofapproximately 365 decitex.
 13. A fabric according to claim 1, whereinthe composite yarn comprises up to approximately 50% of the reinforcingfilament.
 14. A fabric according to claim 1, wherein the composite yarncomprises up to approximately 75% of the polyolefin filament.
 15. Afabric according to claim 1, wherein the composite yarn comprises up toapproximately 50% of the polyester filament.
 16. A fabric according toclaim 1, wherein the composite yarn comprises approximately 12.5% of thereinforcing filament.
 17. A fabric according to claim 1, wherein thecomposite yarn comprises approximately 52.5% of the polyolefin filament.18. A fabric according to claim 1, wherein the composite yarn comprisesapproximately 35% of the polyester filament.
 19. A fabric according toclaim 1, wherein the reinforcing filament is a fiberglass filament or ametal filament.
 20. A fabric according to claim 19, wherein the metalfilament is a stainless steel filament.
 21. A fabric according to claim19, wherein the fiberglass filament possesses a Denier in the range 25to
 75. 22. A fabric according to claim 19, wherein the fiberglassfilament possess a Denier of approximately
 50. 23. A fabric according toclaim 1, wherein the polyolefin filament possesses a Denier in the range200 to
 250. 24. A fabric according to claim 1, wherein the polyolefinfilament possesses a Denier of approximately
 215. 25. A fabric accordingto claim 1, wherein the polyester filament possesses a Denier in therange 50 to
 100. 26. A fabric according to claim 1, wherein thepolyester filament possesses a Denier of approximately
 70. 27. A fabricaccording to claim 1, wherein the sandwich structure of the fabric isselected from a group consisting of a weft knitted sandwich structure, awarp knitted sandwich structure and a flat bed knitted sandwichstructure.
 28. A fabric according to claim 1, wherein the fabric has aweight in the range 300 to 350 g/m².
 29. A fabric according to claim 1,wherein the fabric exhibits a blade cut resistance of level 5 on theEN388:2003 6.2 scale.
 30. An item of clothing comprising a fabricaccording to claim
 1. 31. An item of clothing according to claim 30,wherein the fabric comprised in the item of clothing is arranged suchthat an inner surface of the item of clothing configured to be incontact with a wearer is predominantly comprised of the para-aramid yarnand an opposite outer surface of the item of clothing is predominantlycomprised of the composite yarn.
 32. A method for producing acut-resistant knitted fabric comprising knitting a para-aramid yarn anda composite yarn comprised of a reinforcing filament, a polyolefinfilament and a polyester filament to provide said fabric with a sandwichknit structure.
 33. A method according to claim 32, wherein the yarnsare knitted employing a method selected from a group consisting of weftknitting, warp knitting and flat bed knitting.
 34. A method according toclaim 32, wherein the yarns are knitted in a single or double jerseystyle.
 35. A method according to claim 32, wherein at least one of theyarns is produced using a method selected from a group consisting ofring spinning, core spinning, wrapping and folding.
 36. A methodaccording to claim 32, wherein at least one of the yarns is dyed priorto knitting.
 37. A method according to claim 32, wherein the methodcomprises the step of washing the fabric at a temperature of up toapproximately 130° C.
 38. A method according to claim 32, wherein themethod comprises the step of washing the fabric at a temperature ofapproximately 100° C.